ir_fuel

I had to do a video comparison analysis from what seemed to be an incredibly fast lap around Spa with a standard Cayman GT4. My friend wondered where the car was faster than a Lotus Exige V6 so I took a fast lap video of his Exige and started comparing.

The GT4 was only driven for a few laps in that stint. So an out lap, a fast lap, a really fast lap and back in the pits. I split the video into separate laps with my tool and that's when it struck me. The below image shows the last frame of each lap, according to the laptimer that's rendered in the overlay. Mind you we are talking 30 fps video here, so you can't be more precise than 0.03 seconds, but still ... I guess the images speak for themselves.

Spyerx

Maybe or maybe its video issues?

Around here my solo dl is within a few 100s of mylaps transponder times. Pretty close. And close enough for my liking.

ProCoach

Yes, the VBOX, if it loses GPS speed measure, doesn't have a distance measure. Also, I've had video codecs do that, too.

ir_fuel

It's not a video issue. The video length corresponds to the lap time indicated. It's the start finish marker that moves back. We are talking 0.5 seconds a lap here. That's no a small deviation.

ir_fuel

I don't see how a video codec can cause this.

Just goes to show that even a video with an embedded lap time doesn't always tell the truth. That 2.44.x is actually a 2.45.X upon closer inspection.

Matt Romanowski

So when it makes this error, is there any way to reconcile the actual lap time outside of the video display? Forgive my ignorance of Circuit Tools, but there is no data file, correct?

ProCoach

There is a data file, a .vbo, that is synced with every video made by this equipment. Same file name, two files in each "media" folder for each run.

While I have seen lap times differ slightly in the CT2 window by hundredths, sometimes rounded to tenths (I only specify two decimals), not sure I've ever seen this variance unless here was a split or altered s/f in the .cir file.

I'll add that there is a latency, although less than a SmartyCam HD, between the measures rendered in the video and the values on the accompanying data file. That's why you ALWAYS go with the measures in the data file, be it .drk, .xrk, .ld or .vbo, over anything shown on the video...

Matt Romanowski

So when there is a time discrepancy like this, does the data show a different lap time than the video? I have ways to check the accuracy of start finish in AiM files.

It would be interesting to see if this was caused by a GPS problem, video problem, data problem, etc.

Does CT export to a KML file?

ProCoach

Yes.